Copper-tin multicomponent bronze containing hard phases, production process and use

ABSTRACT

The invention relates to a copper-tin multicomponent bronze consisting of (in % by weight):
         0.5 to 14.0% Sn,   0.01 to 8.0% Zn,   0.01 to 0.8% Cr,   0.05 to 2.0% Al,   0.01 to 2.0% Si,   optionally in addition up to a maximum of 0.1 to 3.0% Mn and   optionally in addition up to a maximum of 0.08% P and   optionally in addition up to a maximum of 0.08% S,   remainder copper and unavoidable impurities,   wherein, in the structure, silicides and/or chromium particles are deposited, which are surrounded by a tin film in the form of a highly tin-containing accumulation.       

     A further aspect of the invention relates to a process for producing strips, plates, bolts, wires, rods, tubes and profiles of the copper-tin multicomponent bronze according to the invention, and also to a use.

The invention relates to a copper alloy based on a copper-tin multicomponent bronze, a production process and the use.

Owing to the greatly increasing mechanical, thermal and corrosive stress of wear-stressed components in modern structures, machines, engines and aggregates, there are more requirements being made of the properties of the alloys suitable for use.

For this reason, the purpose is to develop further the operating properties of the wear-resistant materials. This includes, firstly, increasing the hardness, the strength properties, the temperature resistance of the structure and the complex wear resistance with, at the same time, sufficient toughness properties. Secondly, there is the necessity of any high resistance of the alloy towards corrosive media. In addition, the wear-resistant material must have sufficiently good emergency-running properties which counteract the welding together of the stress partners. To date, for this purpose, particularly, lead-containing copper alloys are used.

Multicomponent bronzes based on copper and tin having other property-defining components are already known. The publication U.S. Pat. No. 6,699,337 B2 discloses copper alloys which, apart from copper, can contain Sn, Ni, P, Zn, Si, Fe, Co, Mg, Ti, Cr, Zr and Al as further elements. The sum of all elements should not exceed a maximum of 30% by weight. The further alloy components are mentioned in general form, without explaining in more detail the respective effect of these alloy components. The possible degree of rolling reduction for coldforming may be derived from the respective element proportion, by relating the tin content and the proportion of the remaining elements to one another via a mathematical relationship.

Further copper-tin alloys are known from DE 10 2006 027 844 A1 of the applicant having tin contents greater than 9% by weight, in which chromium and nickel silicides give rise to a better resistance towards adhesive wear. In particular, the alloy is provided for a use for sliding-bearing elements or for sliding-bearing surfaces in composite components.

The German laid-open application DE 41 26 079 A1 also discloses a casting process using which a broad spectrum of copper alloys may be produced. Inter alia, using this process, copper-tin alloys may be cast having 1 to 11% tin, up to 6% zinc, and the further elements iron, manganese, nickel, chromium, titanium, magnesium and zirconium in smaller proportions. In the production process, a targeted structure condition is set in situ which makes possible immediate further processing by cold rolling.

In addition, copper-tin alloys are known from the publications U.S. Pat. No. 2,128,955 and U.S. Pat. No. 2,128,954 in combination with the further elements Fe, P and Fe, Mn, P. These are alloys which are suitable for hotforming.

In the stated publications, usually also a certain phosphorus content is added for improving the castability. Also, a certain Pb content can be provided for improving the emergency-running properties and also for improved machineability.

As the prior art demonstrates, on account of the broad solidification intervals already present in the binary alloy of copper-tin alloys, by addition of further elements, highly promising property combinations result for differing fields of use of the technique.

The object of the invention is to provide a copper-tin multicomponent bronze having improved cold formability, high strength, hardness, ductility, temperature and corrosion resistance and also having an improved resistance to the wear mechanisms abrasion, adhesion, tribochemical reaction and surface disintegration.

The invention is reflected with respect to a copper-tin multicomponent bronze by the features of Claim 1, with respect to a production process by the features of Claims 10 to 15, and with respect to a use by the features of Claims 16 to 18. The further subsidiary claims relate to advantageous designs and developments of the invention.

The invention includes a copper-tin multicomponent bronze consisting of (in % by weight):

0.5 to 14.0% Sn,

0.01 to 8.0% Zn,

0.01 to 0.8% Cr,

0.05 to 2.0% Al,

0.01 to 2.0% Si,

optionally in addition up to a maximum of 0.1 to 3.0% Mn and

optionally in addition up to a maximum of 0.08% P and

optionally in addition up to a maximum of 0.08% S,

remainder copper and unavoidable impurities,

wherein, in the structure, silicides and/or chromium particles are deposited, which are surrounded by a tin film in the form of a highly tin-containing accumulation.

The invention in this case proceeds from the consideration of providing a copper-tin multicomponent bronze having incorporated Cr-containing and optionally Mn-containing and/or Al-containing monosilicides and mixed silicides and Cr particles which can be produced by the diecasting process or using the continuous or semicontinuous extrusion casting process. Via the deposition of monosilicides and mixed silicides, and Cr particles, the copper-tin multicomponent bronze has a proportion of hard phases which contributes to an improvement of the material resistance to abrasive wear. In addition, the proportion of silicides, owing to a low tendency to wear, gives rise to an improved resistance to adhesive wear. In particular, it must be stated that the alloy, apart from any impurities, does not have any nickel or lead contents.

In contrast to the copper-tin alloy of DE 10 2006 027 844 A1, in the present copper-tin multicomponent bronze according to the invention, an addition of nickel is entirely avoided, and also the P content is restricted to a maximum of 0.08%. Together with the highly important Al proportion of a maximum of 2.0%, this alloy-side measure ensures a significant lowering of the dendritic structure proportion of the Sn-rich δ phase. As a result, this phase is present in a predominantly globular-cluster-type development, which results in a significant improvement, particularly in the toughness properties of the material. In addition, the extent of the porosities in the material is hereby decreased which can develop predominantly in dendrite-rich structure sectors.

In addition, the restriction of the optional P content to a maximum of 0.08% and the addition of A1 to a maximum of 2.0% is associated with a substantial increase in strength and hardness.

The silicides and Cr particles, even during the casting process, and during further processing of the as-cast condition being established, have an important function for structure development. Whereas at least a later annealing is facilitated or reinforced or accelerated by recrystallization of the structure. By means of a sufficiently fine-grain structure, the combination of high strength/hardness and good toughness properties can thereby be achieved.

The content of tin and other elements having a high affinity for oxygen poses particular requirements of the practical procedure of casting copper-tin alloys. For instance, in practice, for ensuring particularly continuous casting operation and also for deoxidation of the melt, the addition of a relatively large content of phosphorus is usual and widespread. The alloy element of phosphorus, however, in the alloy according to the invention increases the structure proportion solidified dendritically, as a result of which the toughness properties of the cast shapes can be impaired. Phosphorus is consequently not added to the alloy or only added in a very small proportion up to a maximum of 0.08% by weight.

A basic concept of the invention is therefore in establishing a balanced ratio of elements forming depositions and therefore promoting separation of Sn such as, for example, Cr, Mn, Al, Si, and elements inhibiting Sn separation such as, for example, Zn in a copper-tin-based material. At the same time, the alloy elements Al and Zn are particularly helpful for ensuring a continuous casting process.

In addition, zinc takes over the forced deoxidation of the melt, in such a manner that the content of phosphorus can at least be decreased, or even entirely omitted. Cast shapes can be produced in this way, having a very uniform, heterogeneous and low-dendrite or even dendrite-free structure.

Via the balanced ratio of said elements forming depositions and therefore promoting Sn separation and elements inhibiting Sn separation in the alloy according to the invention, the solidification interval thereof is in addition substantially decreased. The lower porosity formed thereby contributes substantially to increasing the compressive strength and to improving the complex wear resistance of the wear-protection layer.

Using the alloy composition according to the invention, the cause of formation of an adverse porosity in the alloy can be counteracted. Without this measure, the Sn content of the alloy would have to be lowered. However, the height of the Sn content in the material of the wear-protection layer is important for several reasons:

Tin as alloy element in a copper alloy contributes substantially to lowering the melt temperature. This facilitates, for example, fusion of the alloy onto a base body made of steel for sliding applications.

In addition to lowering the melt temperature, the proportion of the element of tin in the alloy causes an increase in strength and hardness of the material, owing to mixed-crystal solidification, which is further intensified at relatively high tin contents owing to the formation of the Sn-rich δ phase.

The alloy element tin causes a reduced tendency of the copper alloy for gas uptake during the casting or fusion process. As a result, particularly during the fusion of the alloy to a base body made of steel, the development of an open porosity in the wear-protection layer is suppressed, whereby the compressive strength of the component is increased.

In the course of the adhesive wear stress of the component or of the wear-protection layer made of the copper-tin multicomponent bronze according to the invention, the alloy element tin contributes in an important manner to the formation of what is termed a tribolayer between the sliding partners. This mechanism is particularly important under mixed-friction conditions when the emergency-running properties of a material come into the foreground. The tribolayer leads to a reduction of the purely metallic contact surface between the sliding partners, as a result of which fusion or seizing of the system elements is prevented. Therefore the alloy element tin makes an important contribution to replacement of the element lead otherwise used, which should be replaced in future developments for the purpose of environmental protection.

Particularly during the casting or melting process of the alloy according to the invention, in the structure thereof, the mechanism of the proportional Sn separation on the deposited silicides and particles is of importance. This Sn film is a high tin-containing accumulation particularly on the silicides which in any case act as wear carriers in the alloy, effects in the wear-stressed use, via a tribolayer formation, an additional improvement in sliding properties of the silicides and therefore a further increase in resistance of the material to adhesive wear. In other words, the silicides, and if present, the chromium particles, are surrounded by a high tin-containing casing or sheath. Tin phases of this type improve the frictional value in any case improved by silicides and particles by oxide formation. Particular sliding properties of the alloy result therefrom in combination with a low coefficient of friction.

The following effects are assigned to the alloy element aluminum in the copper-tin multicomponent bronze:

Aluminum is of importance for the deposition of silicides in the material and therefore for the increase in component resistance, particularly to the adhesive wear mechanism. The consequence of a more intense silicide deposition in the copper-tin multicomponent bronze is a depletion of the matrix in diverse alloy elements, and also a reduction of the dendrite-like structure proportion of the Sn-rich δ phase, as a result of which the toughness properties of the material are improved.

Owing to the high affinity of aluminum for oxygen, on the surface of the components made of the Al-containing copper-tin multicomponent bronze according to the invention, a compact layer of Al oxide can form very rapidly.

Firstly, the Al oxides assume the function of a covering layer which protects the component from various corrosive media.

Secondly, the Al oxides reinforce what is called the tribolayer on the wear-stressed component surface, which in any case is formed by the Sn and Zn oxides. Therefore, the Al oxides additionally contribute to increasing the resistance of the alloy to adhesive wear.

In principle, an increasing proportion of the element chromium is combined with an increasing content of aluminum, wherein the element content of chromium is below that of the aluminum. The quotient of the element contents Cr/Al extends over an interval from 0.2 to 0.9. The chromium proportion in this case plays an important role in silicide formation which is further increased by the element aluminum.

Owing to the deposition and separation processes during the casting and melting process of the alloy according to the invention, said alloy, depending on the casting process used (diecasting/extrusion casting) and after the fusion to a base body, already possesses in the as-cast condition or fused condition a high level of ductility, from which good cold formability results. In addition, the alloy, owing to the hard phase proportion, has high strength and hardness values, and also a high resistance to abrasive and adhesive wear. With this combination of properties, the subject matter of the invention, even in the as-cast condition, is particularly suitable as a wear-protection layer, which, for example, is melted onto a base body made of steel. In addition, sliding-bearing elements can be produced from the cast of the alloy according to the invention for engines, gears, exhaust gas after-treatment systems, lever and joint systems, hydraulic units or in machines and systems of general mechanical engineering.

In an advantageous embodiment of the invention, the copper-tin multicomponent bronze can consist of (in % by weight):

4.0 to 12.0% Sn,

2.0 to 7.0% Zn,

0.1 to 0.6% Cr,

0.2 to 1.3% Al,

0.1 to 0.6% Si,

optionally in addition up to a maximum of 0.08% P and

optionally in addition up to a maximum of 0.08% S,

remainder copper and unavoidable impurities.

In a further advantageous embodiment of the invention, the copper-tin multicomponent bronze can consist of (in % by weight):

4.0 to 8.0% Sn,

2.0 to 4.0% Zn,

0.1 to 0.5% Cr,

0.1 to 0.8% Al,

0.1 to 0.5% Si,

optionally in addition up to a maximum of 0.08% P and

optionally in addition up to a maximum of 0.08% S,

remainder copper and unavoidable impurities.

In a further advantageous embodiment of the invention, the copper-tin multicomponent bronze can consist of (in % by weight):

2.0 to 10.0% Sn,

1.0 to 7.0% Zn,

0.1 to 0.6% Cr,

0.3 to 2.5% Mn,

0.2 to 1.8% Al,

0.1 to 1.5% Si,

optionally in addition up to a maximum of 0.08% P and

optionally in addition up to a maximum of 0.08% S,

remainder copper and unavoidable impurities.

In a further advantageous embodiment of the invention, the copper-tin multicomponent bronze can consist of (in % by weight):

2.0 to 6.0% Sn,

1.5 to 4.0% Zn,

0.1 to 0.5% Cr,

0.3 to 2.0% Mn,

0.2 to 1.3% Al,

0.1 to 1.3% Si,

optionally in addition up to a maximum of 0.08% P and

optionally in addition up to a maximum of 0.08% S,

remainder copper and unavoidable impurities.

The matrix of the uniform structure of this embodiment consists of ductile α phase and depending on Sn content of the alloy, of proportions of the δ phase. The δ phase, which can be present in dendrite form, leads, owing to its high strength and hardness to the high resistance of the alloy to abrasive wear. In addition, the δ phase, owing to its high Sn content, from which its tendency to formation of a tribolayer results, increases the resistance of the material to adhesive wear. In the matrix, Cr-containing and Mn-containing and Al-containing monosilicides and mixed silicides and also Cr particles are incorporated. This heterogeneous structure consisting of ductile matrix with depositions of great hardness, gives the material an outstanding combination of properties.

Those which may be mentioned in this context are: high strength and hardness values with simultaneously sufficient toughness, adequately good hot and cold formability, high thermal stability of the structure, high corrosion stability, high resistance to the wear mechanisms abrasion, adhesion and surface disintegration.

Advantageously, the matrix of the structure of the copper-tin multicomponent bronze in the as-cast condition, with increasing Sn content of the alloy, depending on the casting/cooling process, can consist of increasing proportions of δ phase (Sn-rich) in otherwise α phase (Sn-poor) of the zinc-containing Cu—Sn mixed crystal types.

In an advantageous embodiment of the invention, in the copper-tin multicomponent bronze, Cr silicides, Al-containing Cr silicides and Cr particles can be incorporated into the matrix of the as-cast condition.

In a further advantageous embodiment of the invention, in the copper-tin multicomponent bronze, Cr silicides, Al-containing Cr silicides, Mn-containing Cr mixed silicides, Mn—Al-containing Cr mixed silicides, Mn silicides, Al-containing Mn silicides and Cr particles can be incorporated into the matrix of the as-cast condition. In addition, the structure of the as-cast condition of the copper-tin multicomponent bronze can be present already having a content of the δ phase up to 60% by volume, of the silicides and the Cr particles up to 20% by volume, and also a remainder α phase.

In a further embodiment of the invention, the copper-tin multicomponent bronze, after a further processing which comprises at least one hotforming or at least one coldforming or at least one hotforming and a coldforming and also optionally further annealing steps, the structure can be present having a content of the δ phase up to 60% by volume, of the silicides and the Cr particles up to 25% by volume, and also a remainder α phase.

Important working examples of the invention are described in more detail with reference to Tab. 1. Cast bolts and cast plates of the copper-tin multicomponent bronze according to the invention were produced by diecasting and extrusion casting. The chemical composition of the casts may be found in Tab. 1.

TABLE 1 Chemical composition of the cast bolts and cast plates Cu Sn Cr Mn Si Zn Al No. [%] [%] [%] [%] [%] [%] [%] Alloy type 1 Residue 6.35 0.36 — 0.16 3.10 0.40 (diecast) Alloy type 2 Residue 7.61 0.40 — 0.27 4.64 0.67 (diecast) Alloy type 3 Residue 9.48 0.32 — 0.15 5.25 0.87 (diecast) Alloy type 4 Residue 8.5 0.28 — 0.27 5.34 0.81 (extrusion cast) Alloy type 5 Residue 9.76 0.33 — 0.18 5.86 0.89 (extrusion cast) Alloy type 6 Residue 10.27 0.23 — 0.18 5.77 0.85 (extrusion cast) Alloy type 7 Residue 4.5 0.28 1.13 0.65 2.3 0.74 (diecast)

After the casting, the mechanical properties of the bolts and plates are at the level which may be found in Tab. 2 in figures for alloy types 2 to 6. Particularly the material characteristics of hardness and elongation at break A5, which is a measure of the ductility of the alloy, can be adapted to the respective component requirements by varying the chemical composition of the copper-tin multicomponent bronze according to the invention and also using a target-directed selection of the casting process.

TABLE 2 Selection of mechanical properties of the cast bolts and cast plates of alloy types 2 to 6 R_(m) R_(p0.2) A5 E HB HBW No. [MPa] [MPa] [%] [GPa] 1/10 1/30 Alloy type 2 337 176 16.2 108 104 111 (diecast) Alloy type 3 379 187 14.4 94 120 126 (diecast) Alloy type 4 382 220 6.6 110 133 145 (extrusion cast) Alloy type 5 391 231 4.3 114 140 152 (extrusion cast) Alloy type 6 399 228 4.7 113 142 154 (extrusion cast)

Independently of the casting process used (diecasting/extrusion casting), the data in Tab. 2 permit conclusions to be drawn about the structure ratios and the mechanical properties of the alloy according to the invention which was fused onto a base body of, e.g. steel. After the fusion, the alloy has a combination of high strength and hardness conforming to requirements, and also sufficient ductility, as has been established for the diecast quality grades type 2 and type 3.

The alloy according to the invention, in one embodiment, can be subjected to a further processing. In this manner, the requirement for improvement of the complex operating properties of the wear-stressed materials is met, since in modern machines, engines, gears, aggregates, structures and plants, there is greatly increasing stress of the system elements. In the course of this further processing, a significant improvement of the toughness properties and/or a substantial increase in tensile strength R_(m), extensibility limit R_(p0.2) and hardness is achieved.

A further aspect of the invention relates to a process for producing strips, plates, bolts, wires, rods, tubes and profiles of the copper-tin multicomponent bronze according to the invention using the diecasting process or the continuous or semicontinuous extrusion casting process.

Advantageously, the further processing of the as-cast condition can comprise carrying out at least one hotforming from 600 to 880° C. Using a hotforming, strips, wires, rods, tubes and profiles can be produced.

A variant of the further processing of the as-cast condition or after a hotforming of the alloy according to the invention includes advantageously at least one annealing treatment in a temperature range from 200 to 880° C. The deposition, separation and conversion processes which in part already take place during the casting process are thereby further intensified. The result is a further improvement of the toughness and strength properties and also an increase in hardness. In addition, the structure, owing to the annealing treatment, is homogenized. This is important for the fields of use in industry, in which, particularly, dynamic cyclic stress and impact stress of the components occurs.

For the use of the copper-tin multicomponent bronze according to the invention, for example as sliding-bearing surfaces on a composite component, optionally, the following heat treatment can be carried out after fusion of the multicomponent bronze to the base body:

Solution annealing at a temperature between 650 and 880° C. with subsequent ageing at a temperature between 350 and 650° C.

The alloy can also be cooled with calmed or accelerated air or water between the solution annealing and the ageing.

For example, the treatment time in the solution annealing is 0.5 to 12 hours. Advantageously, the treatment time in the subsequent ageing annealing is 1 to 12 hours.

By solution annealing with subsequent ageing at elevated temperature, the toughness and strength properties can be significantly improved and the hardness increased. This can be utilized, particularly in combination with a fusion of the copper-tin multicomponent bronze according to the invention, to other materials. For instance, the treatment temperatures (DIN EN 10083-1) for tempering steels (hardening 820 to 860° C., annealing 540 to 660° C.) are in the heat treatment range of the novel multicomponent bronze (solution annealing 650 to 880° C., ageing 350 to 650° C.). This means that, after fusion of the copper alloy to a base body made of tempering steel, the mechanical properties of both composite partners can be optimized in only one treatment step. Apart from the fusion, other joining processes also come into consideration. Those that are conceivable in this context are also forging, brazing and welding on with the optional carrying out of at least one annealing in the temperature range from 200 to 880° C. Likewise, for example composite bearing shells can come into consideration by roll cladding or laser roll cladding of steel strips and strips made of the alloy according to the invention.

A further advantageous possibility of further processing the as-cast condition or of the hot-formed condition or of the annealed as-cast condition or of the annealed hot-formed condition comprises carrying out at least one coldforming. Via this process step, in particular the material parameters R_(m), R_(p0.2) and the hardness are significantly increased. This is important for application cases in which mechanical stressing and/or intense abrasive and adhesive wear stressing of the components occurs.

For the corresponding recrystallization after a coldforming, at least one annealing treatment can be carried out in a temperature range from 400 to 850° C. Firstly, the deposition, separation and conversion processes which in part take place already during the casting process are further intensified thereby. Secondly, via these thermal treatments, a recrystallization of the structure of the alloy according to the invention proceeds. The resultant very fine-grained structure is an important condition in order to produce the combination of properties of high strength and hardness and sufficient toughness of the material.

For a lowering of the residual stresses of the components, advantageously, in addition a stress-relief/ageing annealing can be carried out in a temperature range from 200 to 650° C.

For the fields of use having a particularly severe complex component stressing, a further processing can be selected which comprises a combination of optionally at least one hotforming and at least one coldforming in combination with at least one annealing in a temperature range from 400 to 850° C. and leads to a recrystallization of the structure of the alloy according to the invention. The fine-grain structure of the alloy established in this manner ensures a combination of high strength, high hardness and good toughness properties. In addition, for lowering the residual stresses of the components, a stress-relief annealing treatment can proceed in the temperature range from 200 to 650° C.

Consequence of the strip fabrication in the further processed alloy types 1 and 7 (condition soft):

Combination of coldforming/annealing at the temperature of 750° C./5 h;

with the concluding stress-relief annealing at the temperatures

-   -   450° C./3 h (A)     -   550° C./3 h (B).

After fabrication has been carried out, the mechanical properties of the strips are at the level which is shown in numerical values in Tab. 3. The differentiation for the alloy types 1 and 7 into A and B in each case results from differing stress-relief annealing temperatures at the end of the respective fabrication.

The degrees of deformation and also the temperatures for the recrystallization and stress-relief annealing treatments can be varied in a broad extent in the further processing of the alloy. It is possible thereby to set the mechanical properties in such a manner as is advantageous for the respective use. The form of the further processing described here by way of example and the resultant mechanical properties of the strips in Tab. 3 correspond to the objective of producing strips having a high complex wear resistance and outstanding toughness properties.

TABLE 3 Mechanical properties of the strips (alloy types 1 and 7) Grain size R_(m) R_(p0.2) A5 E HB HBW No. [μm] [MPa] [MPa] [%] [GPa] 1/10 1/30 Alloy type  5 439 239 64 106 107 113 1 A Alloy type 10 433 217 62 116 100 104 1 B Alloy type 5-10 456 253 55 135 113 115 7 A Alloy type 5-10 445 222 59 109 103 105 7 B

The copper-tin multicomponent bronze according to the invention, already in the as-cast condition, and also in the hotformed and annealed condition, has an outstanding cold formability. As a result it is possible by changing the degree of deformation in at least one coldforming to vary in each case the strength and hardness values and also the toughness properties of the alloy according to the profile of requirements in a very large range. For instance, with the choice of a relatively large degree of deformation, the hardness of the material can be set to >200 HBW1/30, for example. For the benefit of improved toughness properties, smaller degrees of deformation lead to correspondingly lower hardness and higher elongation at break values.

The alloy system of the copper-tin multicomponent bronze according to the invention offers the possibility, using a thermal treatment, of effecting phase composition and grain size of the matrix and on the content, density and size of the hard phases and silicides. As a result, it is additionally possible, by changing temperature level and duration of the at least one annealing, to vary the strength and hardness values and also the toughness properties of the alloy, according to requirements, in a very large range. For instance, with the selection of a relatively high annealing temperature and/or annealing time (=soft annealing), the hardness of the material can be set to <100 HB1.0/10. In contrast, it is possible, using a lower annealing temperature and/or annealing time (=stress-relief annealing) to retain substantially the structure condition of the alloy, for example the degree of cold solidification. In this manner, the hardness characteristic can be set to a level >200 HBW1/30.

The copper-tin multicomponent bronze according to the invention can be used, in particular, for sliding-bearing surfaces in composite components, for slide elements in internal combustion engines, gears, exhaust gas after-treatment systems, lever and joint systems, hydraulic units or in machines and systems of general mechanical engineering.

A further use can also be in the field of wear-stressed components in electronics/electrical engineering, e.g. plug-in connectors.

In addition, the copper-tin multicomponent bronze according to the invention can be used for metallic articles in the culture of organisms living in seawater. In particular, the alloy can be used preferably for wear-stressed components of cage systems for maritime fish culture, also known under the term “aquaculture”. The items relate to nets, woven fabrics, braidings and gratings which are produced from wires or metal strips. Rods, profiles or profile tubes for fastening or stabilizing also come into consideration. Likewise, tubes or hollow profiles made of the alloy according to the invention can be used which are used as fastening elements, floats or supply and disposal lines. 

1. Copper-tin multicomponent bronze consisting of (in % by weight): 0.5 to 14.0% Sn, 0.01 to 8.0% Zn, 0.01 to 0.8% Cr, 0.05 to 2.0% Al, 0.01 to 2.0% Si, optionally in addition up to a maximum of 0.1 to 3.0% Mn and optionally in addition up to a maximum of 0.08% P and optionally in addition up to a maximum of 0.08% S, remainder copper and unavoidable impurities, wherein, in the structure, silicides and/or chromium particles are deposited, which are surrounded by a tin film in the form of a highly tin-containing accumulation.
 2. Copper-tin multicomponent bronze according to claim 1, characterized by: 4.0 to 12.0% Sn, 2.0 to 7.0% Zn, 0.1 to 0.6% Cr, 0.2 to 1.3% Al, 0.1 to 0.6% Si, optionally in addition up to a maximum of 0.08% P and optionally in addition up to a maximum of 0.08% S, remainder copper and unavoidable impurities.
 3. Copper-tin multicomponent bronze according to claim 2, characterized by: 4.0 to 8.0% Sn, 2.0 to 4.0% Zn, 0.1 to 0.5% Cr, 0.1 to 0.8% Al, 0.1 to 0.5% Si, optionally in addition up to a maximum of 0.08% P and optionally in addition up to a maximum of 0.08% S, remainder copper and unavoidable impurities.
 4. Copper-tin multicomponent bronze according to claim 1, characterized by: 2.0 to 10.0% Sn, 1.0 to 7.0% Zn, 0.1 to 0.6⁹6 Cr, 0.3 to 2.5% Mn, 0.2 to 1.8% Al, 0.1 to 1.5% Si, optionally in addition up to a maximum of 0.08% P and optionally in addition up to a maximum of 0.08% S, remainder copper and unavoidable impurities.
 5. Copper-tin multicomponent bronze according to claim 4, characterized by: 2.0 to 6.0% Sn, 1.5 to 4.0% Zn, 0.1 to 0.5% Cr, 0.3 to 2.0% Mn, 0.2 to 1.3% Al, 0.1 to 1.3% Si, optionally in addition up to a maximum of 0.08% P and optionally in addition up to a maximum of 0.08% S, remainder copper and unavoidable impurities.
 6. Copper-tin multicomponent bronze according to claim 1, characterized in that the matrix of the structure in the as-cast condition, with increasing Sn content of the alloy, consists of increasing proportions of δ phase (Sn-rich) in otherwise α phase (Sn-poor) of the zinc-containing Cu—Sn mixed crystal types.
 7. Copper-tin multicomponent bronze according to claim 1, characterized in that Cr silicides, Al-containing Cr silicides and Cr particles are incorporated into the matrix of the as-cast condition.
 8. Copper-tin multicomponent bronze according to claim 4, characterized in that Cr silicides, Al-containing Cr silicides, Mn-containing Cr mixed silicides, Mn—Al-containing Cr mixed silicides, Mn silicides, Al-containing Mn silicides and Cr particles are incorporated into the matrix of the as-cast condition.
 9. Copper-tin multicomponent bronze according to claim 1, characterized in that, after a further processing which comprises at least one hotforming or at least one coldforming or at least one hotforming and a coldforming and also optionally further annealing steps, the structure is present having a content of the δ phase up to 60% by volume, of the silicides and the Cr particles up to 20% by volume, and also a remainder α phase.
 10. Process for producing strips, plates, bolts, wires, rods, tubes and profiles of a copper-tin multicomponent bronze according to claim 1 using the diecasting process or the continuous or semicontinuous extrusion casting process.
 11. Process according to claim 10, characterized in that the further processing of the as-cast condition comprises carrying out at least one hotforming in the temperature range from 600 to 880° C.
 12. Process according to claim 10, characterized in that at least one annealing treatment is carried out in a temperature range from 200 to 880° C.
 13. Process according to claim 10, characterized in that the further processing of the as-cast condition or of the hot-formed condition or of the annealed as-cast condition or of the annealed hot-formed condition comprises carrying out at least one coldforming.
 14. Process according to claim 13, characterized in that at least one annealing treatment is carried out in a temperature range from 400 to 850° C.
 15. Process according to claim 13, characterized in that a stress-relief annealing/ageing annealing is carried out in a temperature range from 200 to 650° C.
 16. Use of the copper-tin multicomponent bronze according to claim 1 for sliding-bearing surfaces in composite components, for slide elements in internal combustion engines, gears, exhaust gas after-treatment systems, lever and joint systems, hydraulic units or in machines and systems of general mechanical engineering.
 17. Use of the copper-tin multicomponent bronze according to claim 1 for construction elements in electronics/electrical engineering.
 18. Use of the copper-tin multicomponent bronze according to claim 1 for metallic articles in the culture of organisms living in seawater. 